Recently, with the aim of improving durability of sun screen, foundation, lipstick, etc., technologies of formulating water-repellent compounds and water-repellent pigments into preparations have been greatly developed. As a water-repellent compound, a fluorine compound such as perfluoro-polyether, a silicone compound such as dimethylsiloxane, fluorine-modified silicone resin have been used. Furthermore, as a water-repellent pigment, a fine particle titanium oxide which has been treated with silicone or with metallic soap, etc. have been used. Since these materials have strong resistance to water or perspiration, preparations formulated with these materials exhibit properties of materials such as water-repellency.
For example, the present inventors reported in Japanese Unexamined Patent Publication No. Hei 9-12431 that a cosmetic composition superior in durability can be obtained by formulating a fluorine-modified silicone resin with excellent water and oil repellency. They also reported in Japanese Unexamined Patent Publication No. Hei 7-126126 that a cosmetic composition in which perfluoro-alkyl/polyoxyalkylene-comodified organopolysiloxane and fluoridized powder are formulated is excellent in durability. These technologies are based on the idea that “when each material is excellent in resistance to water, then the durability of the preparations is enhanced.”
Meanwhile, an attempt to enhance sunburn protection performance has been continued in sun screens. They have technically taken over the above-described concept. As are shown in Japanese Unexamined Patent Publication Nos. Sho 61-65808, Hei 6-135817 and Hei 5-339125, techniques of how to formulate materials excellent in durability are centered on. It should be noted that in any of these patents, there are only such expressions as “enhance durability” and “improve lastingness.”
The present inventors have conducted field tests of products in which materials capable of enhancing such durability are formulated. As a result, they have found that products whose durability was supposed to be improved are still poor in actual performance, particularly when worn in water bathing, unexpected poor durability has been confirmed. For example, with some preparations of SPF 100 level, the ultraviolet ray protective function lasted only two to three hours when worn in water. Therefore, there seemed to be a limit to coping merely by the conventional technology of enhancing the durability by combinating water-resistant materials. Particularly for use at a leisure time, a new technical approach has been required in order to impart lastingness to the preparations so as to prevent the skin from being sunburnt all day without the need to reapply the preparations once they are applied in the morning. Although foundations and eye shadow with durability for daily life have been developed, there is the problem that they easily come off in water bathing such as a swimming pool. Thus, preparations which can be used at a leisure time has been in demand. Furthermore, the water-proof test standard of US FDA is used as an indication of resistance to water. According to the test method, however, there are some cases where some products are allowed to have a sign reading that they are excellent in durability even if a person wearing them are sunburnt in the actual use. Therefore, in areas, such as Japan, where consumers have little awareness of the necessity of reapplying sunscreens, the standard fails to meet the actual situation. Accordingly, with the test results, it cannot be said that the product is excellent in durability.